The invention relates to a method for diagnosing the function of an exhaust gas sensor in an exhaust gas, wherein the exhaust gas is at least temporarily brought to an operating temperature during a heating phase by heating with an electric heater.
The invention also relates to a device for carrying out the method.
Exhaust gas sensors are used, for example, in the form of particle sensors for on-board diagnosis of particle filters in the exhaust gas of internal combustion engines. For this purpose, the exhaust gas is fed past an electrode structure of the particle sensor and the change in the impedance between the electrodes as a result of the particles accumulated from the exhaust gas is evaluated.
Such a particle sensor is known, for example, from document DE 10 2007 060 939 A1. Two interdigital electrodes which engage one in the other are applied to an insulating carrier and form the sensor element which is connected to a control device. During a measuring phase, soot is deposited on the electrodes. The particle content of the exhaust gas can be determined from the chronological profile of the change in impedance which is brought about thereby. If the particle sensor is loaded with soot to such an extent that a further change in impedance no longer takes place, said soot is burnt off during a regeneration phase. During this heating phase, the particle sensor is heated using an integrated heating element.
During the regeneration it is known to determine the temperature of the particle sensor using an integrated temperature sensor and to set it using a heating regulator.
Step DE 10 2010 027 975 A1 describes a method for self-diagnosis of an exhaust gas probe which has a heating element, wherein the exhaust gas probe can be a particle sensor. In order to diagnose the exhaust gas probe, the measured heating power of the heating element is compared with a modeled heating power. In the event of a deviation which is greater than a predefined value, the exhaust gas probe is detected as being faulty. The self-diagnosis permits defective particle sensors whose electrodes have been damaged to be detected and corresponding visual or audible warning signals to be emitted.
An object of the invention is to make available a method with which the function of an exhaust gas sensor can be detected easily and reliably.
It is furthermore an object of the invention to make available a device for carrying out the method.